1. Field of the Invention
The present invention relates generally to a communication system, and in particular, to a system and method for transmitting/receiving resource allocation information in a communication system.
2. Description of the Related Art
In the next generation communication system, active research is being conducted to provide high-speed services having various qualities-of-service (QoS). Particularly, in the next generation communication system, active research is being carried out to support high-speed service so as to guarantee mobility and QoS for a Broadband Wireless Access (BWA) communication system such as a Local Area Network (LAN) system and a Metropolitan Area Network (MAN) system. An Institute of Electrical and Electronics Engineers (IEEE) 802.16a/d standard based communication system and an IEEE 802.16e standard based communication system are the typical BWA communication systems.
A description will now be made of an operation of transmitting/receiving resource allocation information, for example, MAP Information Element (IE), in the IEEE 802.16e communication system.
The IEEE 802.16e communication system has a frame structure, so that a base station (BS) efficiently allocates resources of each frame to mobile stations (MSs) and transmits the resource allocation information to the MSs through a MAP message. Herein, a MAP message for transmitting downlink (DL) resource allocation information is called a “DL MAP message,” and a MAP message for transmitting uplink (UL) resource allocation information is called a “UL MAP message.”
If the BS transmits the downlink resource allocation information and the uplink resource allocation information through the DL MAP message and the UL MAP message in this way, each of the MSs decodes the DL MAP message and the UL MAP message transmitted by the BS, to thereby detect an allocated position of the resources allocated to the MS and control information of the data the MS should receive. By detecting the resource allocation position and the control information, the MS can receive and transmit the data through the downlink and the uplink.
The MAP message includes different MAP IE formats according to whether the MAP is a downlink or an uplink, whether the data burst type of the MAP IE is a Hybrid Automatic Repeat reQuest (HARQ) data burst or a non-HARQ data burst, and whether the MAP IE is control information. Therefore, the MS needs to be aware of the format of each MAP IE in order to decode the MAP IE. Each MAP IE can be distinguished using a Downlink Interval Usage Code (DIUC), for the downlink, and an Uplink Interval Usage Code (UIUC), for the uplink. FIG. 1 is a diagram illustrating a frame structure for a general IEEE 802.16e communication system.
Referring to FIG. 1, the frame includes a downlink sub-frame 100 and an uplink sub-frame 150. The downlink sub-frame 100 includes a preamble field 111, a Frame Control Header (FCH) field 113, a DL MAP message field 115, a UL MAP message field 117, and a plurality of DL Burst fields of a DL Burst #1 119-1, a DL Burst #2 119-2, a DL Burst #3 119-3, a DL Burst #4 119-4, and a DL Burst #5 119-5. The uplink sub-frame 150 includes a plurality of control channel fields 151-1, 151-2, and 151-3, and a plurality of UL Burst fields of a UL Burst #1 153-1, a UL Burst #2 153-2, and a UL Burst #3 153-3.
The preamble field 111 is used for transmitting a synchronization signal, i.e. a preamble sequence, for acquiring synchronization between a transmitter and a receiver, i.e. between a BS and an MS. The FCH field 113 is used for transmitting basic information on sub-channel, ranging, and modulation scheme. The DL MAP message field 115 is used for transmitting a DL MAP message, and the UL MAP message field 117 is used for transmitting a UL MAP message.
The DL MAP message field 115 includes a plurality of IEs, i.e. a first IE (IE#1) 115-1, a second IE (IE#2) 115-2, a third IE (IE#3) 115-3, a fourth IE (IE#4) 115-4, and a fifth IE (IE#5) 115-5. The first IE 115-1 includes information on the DL Burst #1 119-1, the second IE 115-2 includes information on the DL Burst #2 119-2, the third IE 115-3 includes information on the DL Burst #3 119-3, the fourth IE 115-4 includes information on the DL Burst #4 119-4, and the fifth IE 115-5 includes information on the DL Burst #5 119-5.
The UL MAP message field 117 includes a plurality of control channel IEs 117-1, 117-2 and 117-3, and a plurality of IEs, i.e. a first IE (IE#1) 117-4, a second IE (IE#2) 117-5, and a third IE (IE#3) 117-6. The control channel IE 117-1 includes information on the control channel field 151-1, the control channel IE 117-2 includes information on the control channel field 151-2, and the control channel IE 117-3 includes information on the control channel field 151-3. The first IE 117-4 includes information on the UL Burst #1 153-1, the second IE 117-5 includes information on the UL Burst #2 153-2, and the third IE 117-6 includes information on the UL Burst #3 153-3.
The DL Burst #1 119-1 to the DL Burst #5 119-5 are used for transmitting corresponding downlink data bursts, the control channel IEs 151-1, 151-2 and 151-3 are used for transmitting corresponding uplink control channel signals, and the UL Burst #1 153-1 to the UL Burst #3 153-3 are used for transmitting corresponding uplink data bursts.
The MS receives the DL MAP message and the UL MAP message, and decodes the received DL MAP message and UL MAP message to detect an IE, i.e. a MAP IE, that indicates information on the resources allocated thereto, thereby detecting a field of the resources allocated to the MS. Herein, each of the IEs included in the DL MAP message expresses its allocated position with its start time and size in the time domain and the frequency domain, and each of the IEs included in the UL MAP message expresses its allocated position as a multiple of a slot with its start time and size. The term “slot” refers to a minimum resource allocation unit composed of a sub-channel and a symbol.
The MS, upon receipt of a DL MAP message, sequentially decodes MAP IEs included in the DL MAP message. If the MS detects a MAP IE allocated to the MS in the course of decoding the MAP IEs, the MS can determine a position of the resources allocated to the MS using position information of the detected MAP IE. In addition, if the MS, upon receipt of a UL MAP message, adds up the fields occupied by all MAP IEs before detecting a MAP IE allocated to the MS, a position of the next field is a location of the MAP IE allocated to the MS itself. This will be described below with reference to FIG. 1.
If the third IE 117-6 included in the UL MAP message is information allocated to a corresponding MS, the amount of resources allocated to the MS corresponds to the resource allocation information appearing in the third IE 117-6 beginning from a part except for an occupied field, or slots, of the UL Burst #1 153-1 associated with the first IE 117-4 and an occupied field, or slots, of the UL Burst #2 153-2 associated with the second IE 117-5.
As described above, the IEEE 802.16e communication system can classify data bursts into an HARQ data burst and a non-HARQ data burst according to whether the HARQ scheme is applied thereto. Basically, the HARQ scheme is similar to an Automatic Repeat reQuest (ARQ) scheme of a Medium Access Control (MAC) protocol. In the HARQ scheme, a transmitter receives an Acknowledgement (ACK)/Non-Acknowledgement (NACK) signal for its transmission data, being fed back from a receiver, and retransmits the transmission data upon receipt of the NACK signal being fed back from the receiver, thereby increasing reliability of the transmission data. The receiver feeds back the ACK signal to the transmitter upon successful receipt of the data transmitted by the transmitter. The receiver feeds back the NACK signal to the transmitter upon failure to receive the data transmitted by the transmitter, i.e. upon detecting an error in the data transmitted by the transmitter.
To use the HARQ scheme in the downlink, the BS should allocate a field with which the MS will transmit the ACK/NACK signal in the uplink, in order to receive the ACK/NACK signal for its transmission data. In addition, to use the HARQ scheme in the uplink, the BS provides the information on the data the MS will retransmit and on the interval where the MS will retransmit the data, replacing a feedback operation of the ACK/NACK signal, or replacing a feedback operation of the ACK/NACK signal through a DL HARQ ACK IE.
For each of the downlink and the uplink, the HARQ scheme is divided into a total of 7 modes, i.e. an HARQ chase mode, an HARQ Incremental Redundancy (IR) mode, an HARQ IR Convolutional Turbo Coding (CTC) mode, an HARQ IR Chase Combining (CC) mode, a Multiple Input Multiple Output (MIMO) HARQ chase mode, a MIMO HARQ IR CC mode, and a MIMO HARQ Space Time Coding (STC) mode.
The MS selects a possible mode supportable by the MS from among the 7 modes through an operation of negotiating the basic capability of the MS with the BS, i.e. an operation of exchanging with the BS a Subscriber Station's Basic Capability Negotiation Request (SBC-REQ) message and a Subscriber Station's Basic Capability Negotiation Response (SBC-RSP) message with the BS.
In order to support the HARQ scheme, the BS includes MAP IEs supporting the HARQ scheme, i.e. an HARQ DL MAP IE and an HARQ UL MAP IE, in the DL MAP message, and transmits the DL MAP message. Then the MS decodes the HARQ DL MAP IE and the HARQ UL MAP IE, and detects DL HARQ burst information and UL HARQ burst information for the MS.
The HARQ DL MAP IE includes information on a downlink HARQ burst, and the HARQ UL MAP IE includes information on an uplink HARQ burst. The HARQ DL MAP IE and the HARQ UL MAP IE each include 7 sub-burst IEs for each individual mode. Each of the sub-burst IEs indicates a data burst position for the MS supporting the corresponding mode. For the downlink, the MS receives information on the interval in which the MS can feed back an ACK/NACK signal for the downlink HARQ bursts, i.e. information on all channels over which the MS can feed back the ACK/NACK signal, from the BS over an HARQ ACK Region Allocation IE. In all the channels, the position where the corresponding MS feeds back the ACK/NACK signal is determined depending on the order of receiving a position of an HARQ ACK enabled downlink HARQ burst (hereinafter referred to as an “HARQ ACK enabled downlink burst”). For convenience, a channel used for feeding back the ACK/NACK signal will be referred to herein as an “ACK channel.” For example, an MS receiving an nth HARQ ACK enabled downlink burst feeds back an ACK/NACK signal for the nth HARQ ACK enabled downlink burst over an nth ACK channel among all the ACK channels notified by the HARQ ACK Region Allocation IE. The HARQ ACK enabled downlink burst is determined depending on an ACK disable bit value in each sub-burst IE, and a value of the ACK disable bit is set to ‘0’ indicates that an ACK channel for ACK/NACK signal feedback is allocated to the MS receiving the corresponding downlink HARQ burst. On the contrary, value of the ACK disable bit is set to ‘1’ indicates that an ACK channel for ACK/NACK signal feedback is not allocated to the MS receiving the corresponding downlink HARQ burst. The MS determines whether the received downlink HARQ burst is an HARQ ACK enabled downlink burst, based on the ACK disable bit, and if it is determined that the received downlink HARQ burst is the HARQ ACK enabled downlink burst, the MS feeds back the ACK/NACK signal over the corresponding ACK channel among all the ACK channels taking into account the order of the HARQ ACK enabled downlink burst. Of course, if the value of the ACK disable bit is set to ‘1’, the MS does not feed back the ACK/NACK signal because no ACK channel is allocated thereto.
A format of the HARQ DL MAP IE is shown in Tables 1A and 1B.
TABLE 1ASizeSyntax(bits)NotesHARQ DL MAP IE {——Extended-2 DIUC4HARQ DL MAP IE( ) = 0x07LENGTH8Length in bytesRCID_Type20b00 = Normal CID 0b01 =RCID11 0b10 = RCID70b11 = RCID3Reserved2While (data remains) {——  Region_ID use indicator10: not use Region_ID 1: useRegion_ID If (Region_ID use indicator == 0) {  OFDMA symbol offset8Offset from the start symbolof DL subframe  Subchannel offset7—  Number of OFDMA symbols7—  Number of subchannels7—Reserved3} else {
TABLE 1BSizeSyntax(bits)NotesRegion_ID8Index to the DL region definedin DL region definition TLV inDCD}Mode4Indicates the mode of this IE0b0000 = Chase HARQ0b0001 = Incrementalredundancy HARQ for CTC0b0010 = Incrementalredundancy HARQ forConvolutional Code 0b0011 = MIMOChase H-ARQ 0b0100 = MIMOIR H-ARQ 0b0101 = MIMOIR H-ARQ forConvolutional Code 0b0110 = MIMOSTC H-ARQ 0b0111-0b1111ReservedBoosting3000; normal (not boosted);001; +6dB; 010; −6dB; 011;+9dB; 100; +3dB; 101; −3dB; 110;−9dB; 111; −12dB;If (Mode == 0b0000) {—— DL HARQ Chase sub-burstvariable—IE ( )  } else if (Mode == 0b0001) {—— DL HARQ IR CTC sub-burst IEvariable—( )  } else if (Mode == 0b0010) {—— DL HARQ IR CC sub-burst IE ( )variable—  } else if (Mode == 0b0011) {MIMO DL Chase H-ARQ Sub-BurstvariableIE ( )  } else if (Mode == 0b0100) {MIMO DL IR H-ARQ Sub-Burst IEvariable( )  } else if (Mode == 0b0101) {MIMO DL IR H-ARQ for CC Sub-variableBurst IE ( )  } else if (Mode == 0b0110) {MIMO DL STC H-ARQ Sub-BurstvariableIE ( )}——}——PaddingvariablePadding to byte; shall be set to 0}—
A format of the HARQ UL MAP IE is shown in Tables 2A to 2C.
TABLE 2ASizeSyntax(bits)NotesHARQ UL MAP IE( ) {——Extended-2 UIUC4HARQ UL MAP IE ( ) = 0x07Length8Length in bytesRCID_Type20b00 = Normal CID 0b01 =RCID110b10 = RCID7 0b11 = RCID3Reserved2while (data remains) {——
TABLE 2BSizeSyntax(bits)NotesAllocation Start Indication10: No allocationstartinformation 1: Allo-cation start informa-tion followsIf(Allocation Start Indication ==1) {——OFDMA Symbol offset8This value indicatesstartSymbol offset ofsubsequent sub-bursts in this HARQUL MAP IESubchannel offset7This value indicatesstartSubchannel offset ofsubsequent sub-bursts in thisHARQ UL MAP IEReserved1}——Mode3Indicates the modeof thisIE 0b000 = ChaseHARQ0b001 = Incre-mental redundancyHARQ for CTC0b010 = Incre-mental redundancyHARQ for Convolu-tional code 0b011 =MIMO Chase H-ARQ 0b100 =MIMO IR H-ARQ0b101 =MIMOIR H-ARQ forConvolutional Code0b110 =MIMOSTC H-ARQ0b111=ReservedN sub Burst4Indicates the num-ber ofbursts in this ULMAP IEFor (i=0; i<N Sub-burst; i++) {——If(Mode == 000)—— UL HARQ Chase Sub-Burstvariable—IE ( )} else if (Mode == 001) {—— UL HARQ IR CTC Sub-variable—Burst IE ( )} else if (Mode == 010) {—— UL HARQ IR CC Sub-Burstvariable—IE ( )} else if (Mode == 011) { MIMO UL Chase H-ARQ Sub-variableBurst IE ( )} else if (Mode == 100) { MIMO UL IR H-ARQ Sub-variableBurst IE ( )} else if (Mode == 101) { MIMO UL IR H-ARQ for CCvariableSub-Burst IE ( ) } else if (Mode == 110) {MIMO UL STC H-ARQ Sub-variableBurst IE ( )
TABLE 2CSizeSyntax(bits)Notes}——}——}——PaddingvariablePadding to byte; shall be set to 0}——
In addition, there are downlink sub-burst IEs and uplink sub-burst IEs for each of the 7 modes. For example, a format of sub-burst IEs for the HARQ chase mode, i.e. DL HARQ chase sub-burst IEs, among the downlink sub-burst IEs, is shown in Tables 3A and 3B.
TABLE 3ASizeSyntax(bits)NotesDL HARQ Chase sub-burst IE {——N sub burst[ISI]5Number of sub-bursts inthe 2D regionReserved3Shall be set to zero.For (j=0; j< N sub burst; j++) {——RCID-IE( )variable—Duration10 Duration in slotsSub-Burst DIUC Indicator1If Sub-Burst DIUC Indi-cator is 1, it indicates thatDIUC is explicitly assignedfor this sub-burst.Otherwise, this sub-burstwill use the same DIUCas the previous sub-burstIf j is ( ) thenindicator shall be 1.Reserved1Shall be set, to zero.If(Sub-Burst DIUC Indicator ==1){DIUC4 Repetition Coding Indication20b00—No repetition coding0b01—Repetition coding of2 used 0b10—Repetitioncoding of 4 used 0b11—Repetition coding of 6 usedReserved2Shall be set to zero.}ACID4—AI_SN1—ACK disable1When this bit is “1” noACK channel is allocatedand the SS shall notreply with an ACK. Dedicated DL Control Indicator2LSB #0 indicates inclusionof CQI control LSB #1indicates inclusion ofDedicated DL Control IEIf (LSB #0 of Dedicated DL——Control Indicator == 1) {Duration (d)4A CQI feedback is trans-mitted on the CQI channelsindexed by the (CQIChannel Index) by theSS for 2{circumflex over ( )}(d − 1)frames. If d is 0b0000,deallocates all CQI feed-back when the currentACID is completedsuccessfully. If d is0b1111, the MS shouldreport until the BScommand for the MS tostop If (Duration !=0b0000){
TABLE 3BSizeSyntax(bits)NotesAllocation Index6Index to the channel in aframe the CQI report shouldbe transmitted by the SSPeriod(p)3A CQI feedback is trans-mitted on the CQI channelsindexed by the (CQIChannel Index) by the SSin every 2{circumflex over ( )}p frames.Frame offset3The MS starts reporting atthe frame of which thenumber has the same 3 LSBas the specified frameoffset. If the currentframe is specified, theMS should start reportingin 8 frames.}——}——If (LSB #1 of Dedicated DL——Control Indicator == 1) { Dedicated DL Control IE ( )variable—}——}——}——
In Tables 1A, 1B, 2A to 2C, 3A and 3B, a Syntax field represents a type of each parameter, a Size field represents a size of each parameter, and a Notes field represents a function of each parameter.
With reference to Tables 1A and 1B, a description will now be made of an operation of decoding the HARQ DL MAP IE.
An MS reads a 4-bit Extended-2 DIUC value, and recognizes that a corresponding MAP IE is an HARQ DL MAP IE, if the Extended-2 DIUC value is 7. Thereafter, the MS performs a loop denoted by ‘while(data remains)’ and reads a 3-bit mode value, thereby determining a type of the next sub-burst IE, and decodes the sub-burst IE by applying the format of the sub-burst IE. The MS performs this decoding operation by performing the loop according to the size indicated by an 8-bit Length parameter existing under the Extended-2 DIUC parameter, completing decoding of the HARQ DL MAP IE. The operation of decoding the HARQ DL MAP IE can also be applied to the HARQ UL MAP IE in a similar way.
As described above, in order to decode MAP messages transmitted by a BS, the MS must be informed of a format of each MAP IE included in the MAP messages. As shown in the HARQ DL MAP IE of Tables 1A and 1B and the HARQ UL MAP IE of Tables 2A to 2C, if the MS reads a Mode parameter value indicating a mode of the HARQ scheme, the MS can determine whether the mode is a supportable mode or not. Because the MS has already provided information on STET supportable mode to the BS during an MS's basic capability negotiation operation, the MS is not allocated resources through a sub-burst IE including the information on the insupportable mode.
However, as shown in the HARQ DL MAP IE of Tables 1A and 1B and the HARQ UL MAP IE shown in Tables 2A to 2C, even for a sub-burst IE associated with its unsupportable mode, the MS needs to be informed of a format of the sub-burst IE in order to normally decode the HARQ DL MAP IE and the HARQ UL MAP IE.
In the case where the HARQ DL MAP IE included in the DL MAP message transmitted by the BS includes sub-burst IEs for each of the 7 modes, and the MS can support only one of the 7 modes, the BS, because it allocates information on the MS through the sub-burst IE for the mode supportable by the MS, has no need to decode the remaining 6 sub-burst IEs except for the sub-burst IE for the one supportable mode. In the current IEEE 802.16e communication system, the MS decode not only the sub-burst IEs for its supportable mode but also the sub-burst IEs for its unsupportable mode, in order to normally decode the DL MAP message and the UL MAP message. A format of the sub-burst IE is very complicated, causing an increase in decoding time required for decoding the sub-burst IE.
As described above, the MS should decode MAP messages, i.e. the DL MAP message and the UL MAP message, in order to detect a position of the resources allocated to the MS and the control information. As a result, the time required for decoding the DL MAP message and the UL MAP message affects performance of the MS.
For example, in the downlink, an increase in the time required for decoding the DL MAP message and the UL MAP message causes a time delay, so the MS must store all data related to the time delay. The MS, as it stores all data related to the time delay, needs to include a large-sized storage device, for example, a memory buffer. As another example, in the uplink, as the DL MAP message and the UL MAP message are decoded faster, Medium Access Control (MAC) software can secure the time enough to process the data. Therefore, there is a need for a method for rapidly decoding the UL MAP message and the UL MAP message.